How do I flip a VIDEO in Photo Booth

I wouldn't have posted it if I hadn't tried it out first:

But I still can't spell "not".

If it's not working for you boot into Safe Mode according to Start up your Mac in safe mode - Apple Support and test to see if the problem persists. Reboot normally and test again.

NOTE: Safe Mode boot can take up to nearly twice as long as a normal boot as it's doing the following; 

• Verifies your startup disk and attempts to repair directory issues, if needed

• Loads only required kernel extensions (prevents 3rd party kernel/extensions from loading)

• Prevents Startup Items and Login Items from opening automatically

• Disables user-installed fonts 

• Deletes font caches, kernel cache, and other system cache files

Hello GovtLawyer and welcome to Apple Support Communities. It appears you are having some difficulty with video orientation for clips captured via PhotoBooth.

The PhotoBooth app does not have an option for flipping video. However you can get there by using the Share icon and choosing Add to Photos. Then, open the Photos app and choose the Edit option in the upper right and then the Crop tab at the top of the window. In the sidebar on the right, you'll see an option called Flip which will flip the video orientation.

Photo editing basics in Photos on Mac

Cheers.

Try checking this Edit menu item:

It will file any photo and video when saving for the first time. It won't flip existing photos or videos.